Dissociation of Mycobacterium bovis: Morphology, Biological Properties and Lipids

The article presents the results of investigations concerning the cleavage of avirulent cells from the virulent epizootic strain Mycobacterium bovis (M. bovis) during the 20 month storage at low positive temperatures (2-3C). It was preceded by a 116-fold reinoculation of the suspension of the virulent culture into a dense nutrient medium. Mycobacteria of the detected colonies have acquired new features and properties. It was noted that in the second and subsequent generations, mycobacteria appeared in the form of non-acid resistant grains and short rod-shaped bacteria and L-forms of the protoplastic (spheroplastic) type. The change in morphology was accompanied by the emergence in mycobacteria of the ability to be grown on chemically simple nutrient media. Different morphological forms of mycobacteria were found in the elective dense nutrient medium at 3C and 37C cultivation: at 3C irrespective of the initial morphological forms, non-acid-resistant short rod-shaped bacteria and grains were generated in dynamics; at 37C -L-shaped protoplastic (spheroplastic) type and elementary small bodies. The appearance of the latter in culture has changed the nature of its growth. It is shown that qualitative processes of morphological forms of the biological cycle of mycobacteria occur on the background of quantitative changes in the chemical composition, in particular lipids. The content of total lipids decreased, at the stability of the quality of the fractions of total lipids. Differences in the ratio of unsaturated to saturated fatty acids in pathogenic and non-pathogenic mycobacteria have been established. Long-chain acids with a content of 26-27 carbon atoms, regardless of the temperature of cultivation, disappeared in the dissociative forms. The biological cycle of the development of dissociative M. bovis at different temperatures of cultivation with properties distinct from the parent strain, characterizes the wider possibilities of the investigated microorganism as it is known today.